1. Field of the Invention
The present invention relates to a production process of a structured material having regions different in property. This structured material can be applied to functional devices such as magnetic recording media in particular.
2. Description of the Related Art
Concerning functional devices, there are devices different in property, for example, magnetic property, conductivity, light emitting property, dielectric constant or the like, for every region, such as discrete magnetic recording media, various kinds of wide area sensors, bio sensors and various kinds of composite sensors.
Description is given below taking a magnetic recording medium as an example. With rapidly increasing of information quantities in recent years, it is necessary to improve not only a linear recording density, but also a track recording density in a magnetic recording medium such as a hard disk (HDD) for the purpose of improving a surface recording density. However, when a track width is narrowed for raising the track recording density, seeping out at track ends by a magnetic field spatially diverging out of the tip of a magnetic head and magnetic interference (crosstalk) between adjoining recording tracks occur. The track width is thereby varies. As a result, deterioration of reproduced signals by increase of medium noise becomes a problem.
In order to solve such a problem, there has been proposed a discrete track medium in which recording tracks, which become recording regions, are magnetically separated (“IEEE Transactions on Magnetics”, Vol. 25, No. 5, p. 3381-3383, 1989). The discrete track medium is expected to permit high-density recording because crosstalk between tracks is effectively inhibited even when an interval between the tracks is sufficiently narrowed. This discrete track medium has the merit that a magnetic head can be exactly accessed to an intended magnetic track.
There have also been proposed production processes of discrete track media of various types. As a process accompanied by no microprocessing for the surface of a medium, there have been proposed processes comprising chemically modifying magnetic layers of regions to be regions between tracks to make them non-magnetic. There have been proposed, for example, a process comprising implanting a nitrogen ion into magnetic layers to make them non-magnetic (Japanese Patent Application Laid-Open No. H05-205257), a process comprising halogenating magnetic layers to make them non-magnetic (Japanese Patent Application Laid-Open No. 2002-359138) and techniques such as local annealing by laser irradiation (Japanese Patent Application Laid-Open No. H05-205257 and Japanese Patent Application Laid-Open No. 2002-359138).
According to the processes disclosed in Japanese Patent Application Laid-Open No. H05-205257 and Japanese Patent Application Laid-Open No. 2002-359138, a discrete track medium having properties different for every region can be fabricated. However, these processes may have required a large-scale apparatus and a long time in some cases.
It is thus an object of the present invention to provide a process for producing a structured material having properties different for every region by a simpler method.